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Steven G Morgan - One of the best experts on this subject based on the ideXlab platform.
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Numerical simulations of Larval Transport into a rip-channeled surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the surf zone is not understood. We investigated Larval Transport mechanisms at a ripchanneled beach. Because tracking larvae in the surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding Larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the surf zone. With onshore wind, onshore currents occur near the surface. In the surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven surface currents to the surf zone, then sink in the turbulent surf zone and remain near the bottom while Transported shoreward. In both cases, the Larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the Transport of larvae.
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Behaviorally Mediated Larval Transport in Upwelling Systems
Advances in Oceanography, 2014Co-Authors: Steven G MorganAbstract:Highly advective upwelling systems along the western margins of continents are widely believed to Transport larvae far offshore in surface currents resulting in Larval wastage, limited recruitment, and increased population connectivity. However, suites of Larval behaviors effectively mediate interspecific differences in the extent of cross-shelf migrations between nearshore adult habitats and offshore Larval habitats. Interspecific differences in behavior determining whether larvae complete development in estuaries or migrate to the continental shelf are evident in large estuaries, but they sometimes may be disrupted by turbulent tidal flow or the absence of a low-salinity cue in shallow, low-flow estuaries, which are widespread in upwelling systems. Larvae of most species on the continental shelf complete development in the coastal boundary layer of reduced flow, whereas other species migrate to the mid- or outer shelf depending on how much time is spent in surface currents. These migrations are maintained across latitudinal differences in the strength and persistence of upwelling, in upwelling jets at headlands, over upwelling-relaxation cycles, and among years of varying upwelling intensity. Incorporating Larval behaviors into numerical models demonstrates that larvae recruit closer to home and in higher numbers than when larvae disperse passively or remain in surface currents.
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Numerical simulations of Larval Transport into a rip‐channeled surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi G. Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the surf zone is not understood. We investigated Larval Transport mechanisms at a ripchanneled beach. Because tracking larvae in the surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding Larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the surf zone. With onshore wind, onshore currents occur near the surface. In the surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven surface currents to the surf zone, then sink in the turbulent surf zone and remain near the bottom while Transported shoreward. In both cases, the Larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the Transport of larvae.
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Field test of the behavioral regulation of Larval Transport
Marine Ecology Progress Series, 2013Co-Authors: Holly B. Kunze, Steven G Morgan, Kamazima M. M. LwizaAbstract:The maintenance of marine populations depends on the completion of Larval migrations between adult and Larval habitats, but the ability of microscopic larvae to regulate their movements in such a dynamic environment has been debated. Using a comparative hypothesis testing approach and intensive hourly sampling throughout the water column, we determined the ability of larvae of 6 species with different swimming abilities (2 gastropods, 2 crabs, 2 fishes) to overcome strong tidal mixing during spring tides and regulate their vertical, and hence, horizontal position, in opposing depth-stratified currents in the upper Hudson River estuary, USA. The vertical distributions of nonmotile eggs and swimming larvae generally differed, suggesting that larvae regulated depth. Eggs were passively mixed by tidal currents, but larvae typically aggre- gated in stratified portions of the water column, which fostered retention in the upper estuary. However, the capacity to regulate depth depended on swimming ability and the degree of mixing. In a predominantly mixed tidal environment upstream, mixing overcame most larvae when current velocities were maximal during mid-ebb or mid-flood tides; tidal vertical migrations were not evident for any species, and diel vertical migrations were apparent for only 1 species. In a partially stratified water column downstream, diel vertical migrations were apparent for larvae of 3 of 4 invertebrate species, and tidal vertical migrations were apparent for the 2 fish species. The presence of all Larval stages showed that all species regulated depth sufficiently well to remain in the upper estuary. Regardless of swimming ability, larvae were retained in the estuary by occur- ring near the level of no net motion, even without completing tidal vertical migrations. Continuous profiling of larvae and hydrodynamics is necessary to reveal the ability of larvae to regulate depth in tidal mixing and recruit to adult populations.
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Cross-shelf Larval Migrations Regulating Larval Supply and Connectivity in a Network of Marine Reserves - eScholarship
2013Co-Authors: Steven G Morgan, John LargierAbstract:1. Does Larval Transport and recruitment vary markedly across an upwelling cell? 2. Do interspecific differences in Larval behavior affect Transport and recruitment? 3. How far from natal populations do larvae with different dispersal “strategies” travel at and away from a major upwelling center? 4. How should spatial variation in Larval Transport affect the placement, size, spacing and evaluation of MPAs across upwelling cells?
Claire B Paris - One of the best experts on this subject based on the ideXlab platform.
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The influence of spawning periodicity on population connectivity
Coral Reefs, 2015Co-Authors: Andrew S. Kough, Claire B ParisAbstract:Many coral reef populations exist as discrete habitat patches linked through Larval dispersal into a larger network. On these reefs, organisms spawn periodically and release propagules over a range of frequencies. Biophysical models of Larval Transport examine marine networks, yet particle release frequency needs careful consideration. We describe the time between sequential spawning events as the release interval and define any linkage of modeled larvae between two habitat sites as a connection. We investigate how changing the release interval affects the connectivity networks of three Caribbean species with low- to high-dispersal potential and swimming behavior. We find that spawning periodicity controls the number and persistence of network connections. Further, Larval vertical movement behavior stabilizes the network, significantly increasing connections and connection persistence. This work demonstrates the impact of release interval on connectivity networks and underscores including Larval behavior with realistic spawning periodicity in biophysical models of Larval Transport.
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Numerical simulations of Larval Transport into a rip-channeled surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the surf zone is not understood. We investigated Larval Transport mechanisms at a ripchanneled beach. Because tracking larvae in the surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding Larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the surf zone. With onshore wind, onshore currents occur near the surface. In the surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven surface currents to the surf zone, then sink in the turbulent surf zone and remain near the bottom while Transported shoreward. In both cases, the Larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the Transport of larvae.
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Numerical simulations of Larval Transport into a rip‐channeled surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi G. Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the surf zone is not understood. We investigated Larval Transport mechanisms at a ripchanneled beach. Because tracking larvae in the surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding Larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the surf zone. With onshore wind, onshore currents occur near the surface. In the surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven surface currents to the surf zone, then sink in the turbulent surf zone and remain near the bottom while Transported shoreward. In both cases, the Larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the Transport of larvae.
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Slope-dependent biophysical modeling of surf zone Larval Transport
2013Co-Authors: Atsushi Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Onshore Transport of intertidal invertebrate larvae at a reflective (steep beach slope) and an interme diate (relatively gradual beach slope) beach is modeled. Physical model calculations are conducted with the measured bat hymetry data and averaged wave data obtained during the summer of 2010 at Sand City beach, CA (intermediate beach) an d the summer of 2011 at Carmel River State Beach, CA (reflective beach). The physical model output is then used in a Lagrangian Larval tracking model. Our results show that Larval delivery to the surf zone is higher at the more dissipative beach than at the more reflective beach, and this i s consistent with the Larval recruitment study by S hanks et al. (2010). Also, two possible factors for the successful onsho re Larval Transport on an intermediate beach, turbu lent-dependent sinking behavior and buoyancy of larvae, are not al ways necessary in the case of a reflective beach.
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Multivariate objective analysis of the coastal circulation of Barbados, West Indies: implication for Larval Transport
Deep Sea Research Part I: Oceanographic Research Papers, 2002Co-Authors: Claire B Paris, Robert K. Cowen, Kamazima M. M. Lwiza, Dong-ping Wang, Donald B. OlsonAbstract:A multivariate spatial objective analysis (MVOA) assimilating high spatio-temporal resolution of hydrographic (CTD) and acoustic (ADCP) observations near Barbados provided a comprehensive view of the local surface circulation (0–100 m) during early spring of two consecutive years (1996 and 1997). Significant submesoscale fluctuations of the velocity and salinity fields exhibit a very dynamic environment. In the middle of each cruise, lowsalinity water originating from the Amazon and entrained by a North Brazil Current Ring (NBCR) intruded from offshore and persisted on the west coast of Barbados throughout the rest of the survey. Principal component analysis (PCA) of velocity relative to the vertical structure and temporal factors in the study area demonstrated that the local circulation was mostly baroclinic and was dominated by a strong salinity front impinging on the island and large amplitude current reversals with a periodicity of ca. 20 d. During transition times, indicated by a change of the sign of the amplitude of the empirical orthogonal function (EOF), the flow became barotropic. This situation produced strong southward currents followed by the onset of vertical velocity shear. Most of the flow variability occurred in the upper 40 m of the water column, which was also found to be the depth of penetration of the low-salinity lenses. These results indicate that the NBCR structure was retained during both intrusions. Lagrangian trajectories using the MVOA currents were found to be consistent with in situ drifter trajectories, suggesting that the analyzed flow field is representative of the near-shore circulation. Tracking of particles released in the surface layer (0–20 m) from the reef shows a maximum residence time of 18 d indicating the possibility of Larval retention within the island-scale flow field. Finally, our results suggest that MVOA, within its limitations, is a powerful tool that can be applied elsewhere to infer circulation and Larval Transport, even in situations when forcing is unknown. r 2002 Published by Elsevier Science Ltd.
Robert K. Cowen - One of the best experts on this subject based on the ideXlab platform.
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Vertical migrations of reef fish larvae in the Straits of Florida and effects on Larval Transport
Limnology and Oceanography, 2011Co-Authors: Klaus B. Huebert, Robert K. Cowen, Su SponaugleAbstract:The goals of this study were to measure vertical distributions of pelagic coral reef fish larvae, identify significant vertical migrations, and estimate the effects of vertical migrations between depths with different ambient currents on Larval Transport in the Straits of Florida. Spring, summer, and fall time-series of plankton net tows were conducted at the edge of the Florida Current offshore of Miami. In each time-series the upper 100 m of the water column at a fixed station was sampled repeatedly at 3-h intervals for two diel cycles, with different nets sampling at five discrete depth ranges. Simultaneously, currents-at-depth were recorded by shipboard current profilers. Mean and standard deviation of Larval depth and statistically significant vertical migrations were determined by nonparametric resampling and tree regression techniques. In 10 taxa, larvae showed ontogenic vertical migrations, gradually moving deeper with growth and development. Vertical distributions of six taxa varied between day and night, revealing diel vertical migrations. Larval Transport was estimated by generating progressive vector diagrams from current measurements and Larval vertical distributions. The dominant alongshore component of the Florida Current resulted in rapid Larval Transport through the Straits of Florida, while cross-shore current was an order of magnitude weaker and highly variable. Larvae at depths . 70 m experienced a 15–75% reduction in Transport; thus, deep vertical distributions and downward vertical migrations potentially favor retention and settlement in the Straits of Florida.
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Multivariate objective analysis of the coastal circulation of Barbados, West Indies: implication for Larval Transport
Deep Sea Research Part I: Oceanographic Research Papers, 2002Co-Authors: Claire B Paris, Robert K. Cowen, Kamazima M. M. Lwiza, Dong-ping Wang, Donald B. OlsonAbstract:A multivariate spatial objective analysis (MVOA) assimilating high spatio-temporal resolution of hydrographic (CTD) and acoustic (ADCP) observations near Barbados provided a comprehensive view of the local surface circulation (0–100 m) during early spring of two consecutive years (1996 and 1997). Significant submesoscale fluctuations of the velocity and salinity fields exhibit a very dynamic environment. In the middle of each cruise, lowsalinity water originating from the Amazon and entrained by a North Brazil Current Ring (NBCR) intruded from offshore and persisted on the west coast of Barbados throughout the rest of the survey. Principal component analysis (PCA) of velocity relative to the vertical structure and temporal factors in the study area demonstrated that the local circulation was mostly baroclinic and was dominated by a strong salinity front impinging on the island and large amplitude current reversals with a periodicity of ca. 20 d. During transition times, indicated by a change of the sign of the amplitude of the empirical orthogonal function (EOF), the flow became barotropic. This situation produced strong southward currents followed by the onset of vertical velocity shear. Most of the flow variability occurred in the upper 40 m of the water column, which was also found to be the depth of penetration of the low-salinity lenses. These results indicate that the NBCR structure was retained during both intrusions. Lagrangian trajectories using the MVOA currents were found to be consistent with in situ drifter trajectories, suggesting that the analyzed flow field is representative of the near-shore circulation. Tracking of particles released in the surface layer (0–20 m) from the reef shows a maximum residence time of 18 d indicating the possibility of Larval retention within the island-scale flow field. Finally, our results suggest that MVOA, within its limitations, is a powerful tool that can be applied elsewhere to infer circulation and Larval Transport, even in situations when forcing is unknown. r 2002 Published by Elsevier Science Ltd.
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Springtime ichthyoplankton of the slope region off the north-eastern United States of America : Larval assemblages, relation to hydrography and implications for Larval Transport
Fisheries Oceanography, 2001Co-Authors: Jonathan A. Hare, Michael P. Fahay, Robert K. CowenAbstract:Larval Transport in the slope region off north-eastern North America influences recruitment to juvenile habitats for a variety of fishes that inhabit the continental shelf. In this study, collections of Larval fishes were made during springtime over the continental slope to provide insights into Larval distributions and Transport. Ichthyoplankton composition and distribution mirrored the physical complexity of the region. Three Larval fish assemblages were defined, each with different water mass distributions. A Gulf Stream assemblage was found predominantly in the Gulf Stream and associated with filaments of discharged Gulf Stream water in the Slope Sea. Larvae of this assemblage originated from oceanic and shelf regions south of Cape Hatteras. Several members of this assemblage utilize habitats in the Middle Atlantic Bight (MAB) as juveniles (Pomatomus saltatrix, Peprilus triacanthus) and other members of the assemblage may share this life cycle (Mugil curema, Sphyraena borealis, Urophycis regia). A Slope Sea assemblage was found in all water masses, and was composed of epi- and mesopelagic fish larvae, as well as larvae of benthic shelf/slope residents. Larvae of one member of this assemblage (U. tenuis) are spawned in the Slope Sea but cross the shelf-slope front and use nearshore habitats for juvenile nurseries. A MAB shelf assemblage was found in MAB shelf water and was composed of larvae that were spawned on the shelf. Some of these species may cross into the Slope Sea before returning to MAB shelf habitats (e.g. Enchelyopus cimbrius, Glyptocephalus cynoglossus). Previous studies have examined the effect of warm-core rings on Larval distributions, but this study identifies the importance of smaller-scale features of the MAB shelf/slope front and of filaments associated with Gulf Stream meanders. In combination with these advective processes, the dynamic nature of Larval distributions in the Slope Sea appears to be influenced, to varying degrees, by both vertical and horizontal behaviour of larvae and pelagic juveniles themselves.
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Transport mechanisms of Larval and pelagic juvenile bluefish (Pomatomus saltatrix) from South Atlantic Bight spawning grounds to Middle Atlantic Bight nursery habitats
Limnology and Oceanography, 1996Co-Authors: Jonathan A. Hare, Robert K. CowenAbstract:In this study we examined the mechanisms by which Pomatomus saltatrix (Pisces: Pomatomidae) larvae and pelagic juveniles are Transported from South Atlantic Bight spawning grounds to Middle Atlantic Bight estuarine nursery habitats. Data on Larval and pelagic juvenile distributions, estuarine juvenile recruitment, hydrography, wind speed and direction and satellite-derived, sea surface temperature were used to examine potential Larval Transport mechanisms. On the basis of these analyses, a scenario for northward Transport of P. saltatrix was developed. Gulf Stream-associated flow moves P. saltatrix larvae northeastward from their South Atlantic Bight spawning grounds. Larval Transport from the Gulf Stream to the Middle Atlantic Bight shelf edge occurs in warm-core ring streamers, but some more developed individuals may swim across. Finally, P. saltatrix pelagic juveniles actively swim across the Middle Atlantic Bight shelf, a behavior initiated when the surface shelf-slope temperature front dissipates in late spring. This scenario predicts that the number of South Atlantic Bight-spawned P. saltatrix juveniles entering estuaries (i.e. recruitment) is determined in part by warm-core ring streamer activity. The timing of recruitment, however, is determined almost entirely by the timing of the dissipation of the surface shelf-slope temperature front.
David A. Siegel - One of the best experts on this subject based on the ideXlab platform.
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The tattered curtain hypothesis revised: Coastal jets limit cross-shelf Larval Transport
Limnology and Oceanography: Fluids and Environments, 2014Co-Authors: Cheryl S. Harrison, David A. SiegelAbstract:Exchange and retention of coastal waters modulate dispersal of marine larvae, affecting marine ecosystem dynamics. A hypothesis was put forward in the 1980s describing the coastal upwelling front as a “tattered curtain” that retains larvae. This front was envisioned to be broken up by squirts and eddies, hitting the coast under upwelling relaxation events. Here we revise this hypothesis by using an idealized ocean model of an eastern boundary upwelling current, and an idealized particle/larvae model appropriate for shelf-spawning benthic species. Modeled Larval settlement patterns were controlled by retention in the core of the upwelling jet, bounded by regions of high-velocity shear on the flanks of the jet. Squirts, filaments, poleward-moving eddies, and meanders modulated settlement patterns locally, while dense packets moved equatorward within the upwelling jet. Correlation between settlement (i.e., particles 20–40 d old
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the tattered curtain hypothesis revised coastal jets limit cross shelf Larval Transport
Limnology and Oceanography, 2014Co-Authors: Cheryl S. Harrison, David A. SiegelAbstract:Exchange and retention of coastal waters modulate dispersal of marine larvae, affecting marine ecosystem dynamics. A hypothesis was put forward in the 1980s describing the coastal upwelling front as a “tattered curtain” that retains larvae. This front was envisioned to be broken up by squirts and eddies, hitting the coast under upwelling relaxation events. Here we revise this hypothesis by using an idealized ocean model of an eastern boundary upwelling current, and an idealized particle/larvae model appropriate for shelf-spawning benthic species. Modeled Larval settlement patterns were controlled by retention in the core of the upwelling jet, bounded by regions of high-velocity shear on the flanks of the jet. Squirts, filaments, poleward-moving eddies, and meanders modulated settlement patterns locally, while dense packets moved equatorward within the upwelling jet. Correlation between settlement (i.e., particles 20–40 d old <10 km from shore) and wind was low for a lagged wind product (r=0.33) and moderate for a 20-d integrated wind product (r=0.62). We determined that it is not upwelling relaxation but sustained, moderate upwelling that can result in a highly retentive jet that entrains larvae and acts as a barrier to cross-shelf Transport; however, the amount of retention is highly variable. Settlement was low after strong, persistent upwelling completely tattered the jet. Jet cores in general should act as important retentive Transport barriers across diverse coastal systems, a view supported by dynamical theory, modeling studies, and Larval recruitment observations.
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Model sensitivity and robustness in the estimation of Larval Transport: A study of particle tracking parameters
Journal of Marine Systems, 2013Co-Authors: Rachel D. Simons, David A. Siegel, Kevin S. BrownAbstract:Abstract Many marine organisms spend their early lives as planktonic larvae dispersed by ocean currents. Predictions of Larval Transport are important for a wide range of applications including the interpretation of population genetics, fisheries management, and the planning of no-take marine protected areas. A popular method for predicting Larval Transport is through the use of coupled ocean circulation and particle tracking models, termed “biophysical” models. Although much research has been done on the sensitivity and uncertainty of ocean circulation models, the sensitivity of particle tracking models for the assessment of Larval Transport has been largely overlooked. This study investigates the sensitivity of Larval Transport predictions to three input parameters universally required for particle tracking in biophysical models; namely the number of particles released, the particle release depth, and the particle tracking time. Using a three-dimensional biophysical model of the Southern California Bight, estimates of Larval Transport are quantified using a two-dimensional vertically-integrated particle density distribution (PDD) and the difference between PDDs is assessed using the fraction of unexplained variance (FUV). Overall, our study shows that Larval Transport predictions are sensitive to changes in all three input parameters and that the sensitivity is affected by the strength of mixing in the system. For the number of particles released, the FUV falls off rapidly as the number of particles increases. A minimum number of particles is identified that guarantees robustness of model predictions; this number increases as the complexity of the circulation patterns increases. For the particle release depth, the FUV between PDDs grew linearly as particles are released farther apart. The FUV is also inversely proportional to the strength of vertical mixing as the FUV is smaller in the winter when a deep mixed layer and weak stratification are present and larger in the summer when the system is strongly stratified. For the particle tracking time, the FUV between daily PDDs is much larger for short tracking times of 15 days or less than for longer tracking times of 20 days or more, showing a dependence on the length of time the particles take to be evenly mixed throughout the system. Our study quantifies the parameter sensitivity of Larval Transport predictions and presents a straightforward methodology to achieve robust predictions of Larval Transport from biophysical models.
Ad Reniers - One of the best experts on this subject based on the ideXlab platform.
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Numerical simulations of Larval Transport into a rip-channeled surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the surf zone is not understood. We investigated Larval Transport mechanisms at a ripchanneled beach. Because tracking larvae in the surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding Larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the surf zone. With onshore wind, onshore currents occur near the surface. In the surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven surface currents to the surf zone, then sink in the turbulent surf zone and remain near the bottom while Transported shoreward. In both cases, the Larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the Transport of larvae.
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Numerical simulations of Larval Transport into a rip‐channeled surf zone
Limnology and Oceanography, 2014Co-Authors: Atsushi G. Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Competent larvae of intertidal invertebrates have to migrate toward shore for settlement; however, their migration through the surf zone is not understood. We investigated Larval Transport mechanisms at a ripchanneled beach. Because tracking larvae in the surf zone is infeasible, we used a three-dimensional biophysical model to simulate the processes. The coupled model consists of a physical module for currents and waves, and a biological module for adding Larval traits and behaviors as well as Stokes drift to Lagrangian particles. Model calculations were performed with and without onshore wind forcing. Without wind, wave-driven onshore streaming occurs in the bottom boundary layer outside the surf zone. With onshore wind, onshore currents occur near the surface. In the surf zone, offshore-directed rip currents and compensating onshore-directed currents over shoals are formed in both no-wind and wind cases. In the biological module, neutral, negative, and positive buoyant particles were released offshore. Additionally, particles either sank in the presence of turbulence or not. Two scenarios achieved successful onshore migration: Negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming; positively buoyant larvae drift toward shore in wind-driven surface currents to the surf zone, then sink in the turbulent surf zone and remain near the bottom while Transported shoreward. In both cases, the Larval concentration is highest in the rip channel, consistent with field data. This successful result is only obtained if turbulence-dependent sinking behavior and Stokes drift are included in the Transport of larvae.
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Slope-dependent biophysical modeling of surf zone Larval Transport
2013Co-Authors: Atsushi Fujimura, Alan L. Shanks, Jamie Macmahan, Ad Reniers, Claire B Paris, Steven G MorganAbstract:Onshore Transport of intertidal invertebrate larvae at a reflective (steep beach slope) and an interme diate (relatively gradual beach slope) beach is modeled. Physical model calculations are conducted with the measured bat hymetry data and averaged wave data obtained during the summer of 2010 at Sand City beach, CA (intermediate beach) an d the summer of 2011 at Carmel River State Beach, CA (reflective beach). The physical model output is then used in a Lagrangian Larval tracking model. Our results show that Larval delivery to the surf zone is higher at the more dissipative beach than at the more reflective beach, and this i s consistent with the Larval recruitment study by S hanks et al. (2010). Also, two possible factors for the successful onsho re Larval Transport on an intermediate beach, turbu lent-dependent sinking behavior and buoyancy of larvae, are not al ways necessary in the case of a reflective beach.
